Implantable stimulation devices deliver electrical stimuli to nerves and tissues for the therapy of various biological disorders, such as pacemakers to treat cardiac arrhythmia, defibrillators to treat cardiac fibrillation, cochlear stimulators to treat deafness, retinal stimulators to treat blindness, muscle stimulators to produce coordinated limb movement, spinal cord stimulators to treat chronic pain, cortical and Deep Brain Stimulators (DBS) to treat motor and psychological disorders, and other neural stimulators to treat urinary incontinence, sleep apnea, shoulder subluxation, etc. The description that follows will generally focus on the use of the invention within a Spinal Cord Stimulation (SCS) system, such as that disclosed in U.S. Pat. No. 6,516,227. However, the present invention may find applicability with any Implantable Pulse Generator (IPG) or in any IPG system.
As shown in FIG. 1, a SCS system includes an Implantable Pulse Generator (IPG) 10, which includes a biocompatible device case 12 formed of titanium for example. The case 12 typically holds the circuitry and battery 14 (FIG. 2) necessary for the IPG 10 to function, which battery 14 may be either rechargeable or primary in nature. The IPG 10 is coupled to electrodes 16 via one or more electrode leads 18 (two of which are shown). The proximal ends of the leads 18 include electrode terminals 20 that are coupled to the IPG 10 at one or more connector blocks 22 fixed in a header 24, which can comprise an epoxy for example. Contacts in the connector blocks 22 make contact with the electrode terminals 20, and communicate with the circuitry inside the case 12 via feedthrough pins 26 passing through a hermetic feedthrough 28 to allow such circuitry to provide stimulation to or monitor the various electrodes 16.
In the illustrated embodiment, there are sixteen electrodes 16 split between two leads 18, although the number of leads and electrodes is application specific and therefore can vary. In an SCS application, two electrode leads 18 are typically implanted on the right and left side of the dura within the patient's spinal column. The proximal ends of the leads 18 with the electrode terminals 20 are then tunneled through the patient's flesh to a distant location, such as the buttocks, where the IPG case 12 is implanted, at which point they are coupled to the lead connectors 22.
As shown in FIG. 2, IPG 10 contains a charging coil 30 for wirelessly charging of the IPG's battery 14 using an external charging device 50, assuming that battery 14 is rechargeable battery. If IPG 10 has a non-rechargeable (primary) battery 14, charging coil 30 in the IPG 10 and external charger 50 can be dispensed with. IPG 10 also contains a telemetry coil antenna 32 for wirelessly communicating data with an external controller device 40, also explained further below. In other examples, antenna 32 can comprise a short-range RF antenna such as a slot, patch, or wire antenna. IPG 10 also contains control circuitry such as a microcontroller 34, and one or more Application Specific Integrated Circuit (ASICs) 36, which can be as described for example in U.S. Pat. No. 8,768,453. ASIC(s) 36 can include stimulation circuitry for providing stimulation pulses at one or more of the electrodes 16, and may also include telemetry modulation and demodulation circuitry for enabling bidirectional wireless communications at antenna 32; battery charging and protection circuitry coupleable to charging coil 30; DC-blocking capacitors in each of the current paths proceeding to the electrodes 16, etc. Components within the case 12 are integrated via a printed circuit board (PCB) 38.
FIG. 2 further shows the external components referenced above in plan and cross sections that may be used to communicate with the IPG 10. External controller 40 may be used to control and monitor the IPG 10 via a bidirectional wireless communication link 42 passing through a patient's tissue 5. For example, the external controller 40 may be used to provide or adjust a stimulation program for the IPG 10 to execute that provides stimulation to the patient. The stimulation program may specify a number of stimulation parameters, such as which electrodes are selected for stimulation; whether such active electrodes are to act as anodes or cathodes; and the amplitude (e.g., current), frequency, and duration of stimulation at the active electrodes, assuming such stimulation comprises stimulation pulses as is typical.
Communication on link 42 can occur via magnetic inductive coupling between a coil antenna 44 in the external controller 40 and the IPG 10's telemetry coil 32 as is well known. Typically, the magnetic field comprising link 42 is modulated, for example via Frequency Shift Keying (FSK) or the like, to encode transmitted data. For example, data telemetry via FSK can occur around a center frequency of fc=125 kHz, with a 129 kHz signal representing transmission of a logic ‘1’ bit and 121 kHz representing a logic ‘0’ bit. However, transcutaneous communications on link 42 need not be by magnetic induction, and may comprise short-range RF telemetry (e.g., Bluetooth, WiFi, Zigbee, MICS, etc.) if antennas 44 and 32 and their associated communication circuitry are so configured. The external controller 40 is generally similar to a cell phone and includes a hand-holdable, portable housing.
External charger 50 provides power to recharge the microstimulator's battery 14 (FIG. 1) should that battery be rechargeable. Such power transfer occurs by energizing a charging coil 54 in the external charger 50, which produces a magnetic field comprising transcutaneous link 52, which may occur with a different frequency (f2=80 kHz) than data communications on link 42. This magnetic field 52 energizes the charging coil 30 in the IPG 10, which is rectified, filtered, and used to recharge the battery 14. Link 52, like link 42, can be bidirectional to allow the IPG 10 to report status information back to the external charger 50, such as by using Load Shift Keying as is well-known. For example, once circuitry in the IPG 10 detects that the battery 14 is fully charged, it can cause charging coil 30 to signal that fact back to the external charger 50 so that charging can cease. Like the external controller 40, external charger 50 generally comprises a hand-holdable and portable housing.
External controller 40 and external charger 50 are described in further detail in U.S. Patent Application Publication 2015/0080982. Note also that the external controller 40 and external charger 50 can be partially or fully integrated into a signal external system, such as disclosed in U.S. Pat. Nos. 8,335,569 and 8,498,716.
Implantation of IPG 10 in a patient is normally a multi-step process, as explained with reference to FIG. 3. A first step involves implantation of the distal ends of the lead(s) 18 with the electrodes 16 into the spinal column 60 of the patient through a temporary incision 62 in the patient's tissue 5. The proximal ends of the leads 18 including the electrode terminals 20 extend externally from the incision 62 (i.e., outside the patient), and are ultimately connected to an External Trial Stimulator (ETS) 70. The ETS 70 is used during a trial stimulation phase to provide stimulation to the patient, which may last for two or so weeks for example. To facilitate the connection between the leads 18 and the ETS 70, ETS extender cables 80 may be used that includes receptacles 82 (similar to the connector blocks 22 (FIG. 1) in the IPG 10) for receiving the electrode terminals 20 of leads 18, and connectors 84 for meeting with ports 72 on the ETS 70, thus allowing the ETS 70 to communicate with each electrode 16 individually. Once connected to the leads 18, the ETS 70 can then be affixed to the patient in a convenient fashion for the duration of the trial stimulation phase, such as by placing the ETS 70 into a belt worn by the patient (not shown).
The ETS 70 essentially mimics operation of the IPG 10 to provide stimulation to the implanted electrodes 16. This allows the effectiveness of stimulation therapy to be verified for the patient, such as whether therapy has alleviated the patient's symptoms (e.g., pain). Trial stimulation using the ETS 70 further allows for the determination of particular stimulation program(s) that seems promising for the patient to use once the IPG 10 is later implanted into the patient. Although not shown, the ETS 70 typically contains a battery within its housing along with stimulation and communication circuitry.
The stimulation program executed by the ETS 70 can be provided or adjusted via a wired or wireless link 92 (wireless shown) from a clinician programmer 90. As shown, the clinician programmer 90 comprises a computer-type device, and may communicate wirelessly via link 92 using a communication head or wand 94 wired to the computer. Communication on link 92 may comprise magnetic inductive or short-range RF telemetry schemes as already described, and in this regard the ETS 70 and the clinician's programmer 90 and/or communication head 94 may include antennas compliant with the telemetry means chosen. Clinician programmer 90 may be as described in U.S. Patent Application Publication 2015/0360038. Note that the external controller 40 (FIG. 2) may also communicate with the ETS 70 to allow the patient means for providing or adjusting the ETS 70's stimulation program.
At the end of the trial stimulation phase, a decision is made whether to abandon stimulation therapy, or whether to provide the patient with a permanent IPG 10 such as that shown in FIG. 1. Should it be determined that stimulation therapy is not working for the patient, the leads 18 can be explanted from the patient's spinal column 60 and incision 62 closed in a further surgical procedure.
By contrast, if stimulation therapy is effective, IPG 10 can be permanently implanted in the patient as discussed above. (“Permanent” in this context generally refers to the useful life of the IPG 10, which may be from a few years to a few decades, at which time the IPG 10 would need to be explanted and a new IPG 10 implanted). Thus, the IPG 10 would be implanted in the correct location (e.g., the buttocks), with the proximal ends of leads 18 including electrode terminals 20 tunneled through the tissue 5 and coupled to the connection blocks 22 in the IPG's header 24. Thereafter, temporary incision 62 can be closed, and the ETS 70 dispensed with. The result is fully-implanted stimulation therapy solution. If a particular stimulation program(s) had been determined during the trial stimulation phase, it/they can then be programmed into and executed by the IPG 10, and thereafter modified wirelessly using either the external programmer 40 or the clinician programmer 90.
While trial stimulation can be effective, the inventors have concerns with this approach. In particular, stimulation during the trial stimulation phase requires a temporary incision 62 to allow communications between the implanted electrodes 16 and the external ETS 70. While proper bandaging and antibiotics can help mitigate the risk of infection at the incision 62, it is nonetheless unfortunate that the incision must remain open thought the trial period. Because it is not prudent to allow incision 62 to remain open for an extended period of time, the trial stimulation phase is effectively limited in time by the need to close this incision (typically two weeks or less). In other words, even though it may be desirable in some cases to run trial stimulation for longer periods, the need to close the incision 62 may cut such experimentation short, thus forcing a premature decision whether to proceed with implantation of the IPG 10.
A further concern in the inventors' opinion is the fact that implantation of the IPG 10 is essentially a two-step procedure, requiring implantation of the leads 18, followed just weeks later by permanent implantation of the IPG 10. This is difficult on the patient, who must undergo two surgical procedures in a short period of time.
These problems have caused the inventors to think of new solutions, and specifically fully-implanted solutions in which stimulation therapy can be tried at least temporarily, as disclosed herein.